The present invention relates to a coating method and apparatus by which a coater gap can be set accurately, quickly and easily and further, the reproducing accuracy can be improved.
In an extrusion type or a slide hopper type coating apparatus, the setting of a coater gap between a coater edge and a web is one of the most important factors from the viewpoints of uniformity and stability of coating, and it is also important to improve quality and productivity. However, a method to directly detect the coater edge position has as yet not been proposed.
Conventionally, the coater gap Setting or adjusting operation is conducted by a skilled worker in the following manner before a coating operation is started or when the coating apparatus or coating roller is replaced: the skilled worker adjusts a gap between a coater edge and a web, or a gap between the coater edge and a coating roller using a thickness gauge; or a displacement of the web or coating roller with respect to the frame of the device is measured by a dial gauge or distance sensor mounted on the frame, and the skilled worker adjusts the gap in accordance with the detected value.
However, according to the aforementioned method, the position of the coater edge during coating, that is, the coater gap, can not be detected, and further in the case of replacement of a coating die, the adjusting operation must be carried out again. Therefore, working efficiency is lowered, and there is a possibility that the reproducibility is lowered.
When the coater gap is fluctuated or the coater gap is in an abnormal condition, the coated layer is of inferior quality, that is, streaks and stripes are caused on the coated layer, and further the layer thickness is deviated.
Japanese Patent Application Open to Public Inspection No. 40258/1990 discloses the following means in which the positional sensor is disposed in such a manner that: the angle formed by the positional sensor axis and the horizontal line is the same as that formed by the moving axis of the coating die and the horizontal line. Until now, there has not been proposed a coater edge position detecting means by which the coater edge position can be directly detected so as to stably obtain excellent coating properties.